U.S. patent number 7,410,409 [Application Number 10/018,188] was granted by the patent office on 2008-08-12 for abrasive compound for cmp, method for polishing substrate and method for manufacturing semiconductor device using the same, and additive for cmp abrasive compound.
This patent grant is currently assigned to Hitachi Chemical Co., Ltd.. Invention is credited to Toranosuke Ashizawa, Kouji Haga, Keizou Hirai, Naoyuki Koyama, Youiti Machii, Masato Yoshida.
United States Patent |
7,410,409 |
Koyama , et al. |
August 12, 2008 |
Abrasive compound for CMP, method for polishing substrate and
method for manufacturing semiconductor device using the same, and
additive for CMP abrasive compound
Abstract
The present invention discloses a CMP abrasive comprising cerium
oxide particles, a dispersant, an organic polymer having an atom or
a structure capable of forming a hydrogen bond with a hydroxyl
group present on a surface of a film to be polished and water, a
method for polishing a substrate comprising polishing a film to be
polished by moving a substrate on which the film to be polished is
formed and a polishing platen while pressing the substrate against
the polishing platen and a polishing cloth and supplying the CMP
abrasive between the film to be polished and the polishing cloth, a
method for manufacturing a semiconductor device comprising the
steps of the above-mentioned polishing method, and an additive for
a CMP abrasive comprising an organic polymer having an atom or a
structure capable of forming a hydrogen bond with a hydroxyl group
present on a surface of a film to be polished, and water.
Inventors: |
Koyama; Naoyuki (Tsukuba,
JP), Haga; Kouji (Hitachi, JP), Yoshida;
Masato (Tsukuba, JP), Hirai; Keizou (Hitachiota,
JP), Ashizawa; Toranosuke (Hitachinaka,
JP), Machii; Youiti (Tsuchiura, JP) |
Assignee: |
Hitachi Chemical Co., Ltd.
(Tokyo, JP)
|
Family
ID: |
27323685 |
Appl.
No.: |
10/018,188 |
Filed: |
June 15, 2000 |
PCT
Filed: |
June 15, 2000 |
PCT No.: |
PCT/JP00/03891 |
371(c)(1),(2),(4) Date: |
December 18, 2001 |
PCT
Pub. No.: |
WO00/79577 |
PCT
Pub. Date: |
December 28, 2000 |
Foreign Application Priority Data
|
|
|
|
|
Jun 18, 1999 [JP] |
|
|
11/172821 |
Jul 19, 1999 [JP] |
|
|
11/204842 |
Nov 24, 1999 [JP] |
|
|
11/332221 |
|
Current U.S.
Class: |
451/36;
257/E21.23; 438/693; 451/41; 451/59; 451/63 |
Current CPC
Class: |
C09G
1/02 (20130101); C09K 3/1409 (20130101); H01L
21/31053 (20130101); C09K 3/1463 (20130101); H01L
21/30625 (20130101) |
Current International
Class: |
B24B
1/00 (20060101) |
Field of
Search: |
;216/88,89,90
;438/691,692,693 ;451/36,41,59,63 |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
|
|
|
|
|
|
|
0 373 501 |
|
Jun 1990 |
|
EP |
|
0 820 092 |
|
Jan 1998 |
|
EP |
|
0 846 740 |
|
Jun 1998 |
|
EP |
|
410102040 |
|
Apr 1998 |
|
JP |
|
WO 99/64527 |
|
Dec 1999 |
|
WO |
|
Other References
Supplementary European Search Report, for Application No. EP 00 93
7240, dated Oct. 24, 2002. cited by other.
|
Primary Examiner: Eley; Timothy V
Attorney, Agent or Firm: Antonelli, Terry, Stout &
Kraus, LLP.
Claims
The invention claimed is:
1. A CMP abrasive consisting essentially of cerium oxide particles,
a dispersant, water, and, additionally, an organic polymer having
an atom or a structure capable of forming a hydrogen bond with a
hydroxyl group present on a surface of said film to be polished,
wherein the organic polymer is a compound containing at least one
atom having an unpaired electron in a molecular structure, and
wherein the abrasive is capable of being used in forming shallow
trench isolation, and is adapted to polish an inorganic insulating
film having unevenness on a surface thereof.
2. The CMP abrasive according to claim 1, wherein said organic
polymer is a compound containing either one or both of a nitrogen
atom and an oxygen atom in a molecular structure.
3. The CMP abrasive according to claim 1, wherein said organic
polymer is a compound having an adsorption ratio of 50% or more
with respect to silicon oxide particles of a specific surface area
of 50 m.sup.2/g dispersed in water of pH 6 to 8.
4. The CMP abrasive according to claim 1, wherein said organic
polymer is a compound having an adsorption ratio of 40% or more
with respect to silicon nitride particles of a specific surface
area of 3.3 m.sup.2/g dispersed in water of pH 6 to 8.
5. The CMP abrasive according to claim 1, wherein the sedimentation
speed of the cerium oxide particles is 20 .mu.m/s or less.
6. The CMP abrasive according to claim 1, wherein said organic
polymer is polyvinyl pyrrolidone.
7. The CMP abrasive according to claim 6, wherein said polyvinyl
pyrrolidone has a weight average molecular weight of 5,000 to
1,200,000.
8. The CMP abrasive according to claim 1, which comprises 0.01 to
2.0 parts by weight of a dispersant and 0.001 to 1,000 parts by
weight of an organic polymer based on the cerium oxide particle of
100 parts by weight, and the rest comprising water, the
concentration of the cerium oxide particles in the abrasive being
0.5 to 20% by weight.
9. A method for polishing a substrate comprising polishing by
moving a substrate on which an inorganic insulating film having
unevenness on a surface thereof, to be polished is formed and a
polishing platen while pressing the substrate against the polishing
platen and a polishing cloth and supplying said CMP abrasive for
polishing the inorganic insulating film having unevenness on a
surface thereof according to claim 1, between the inorganic
insulating film to be polished and the polishing cloth.
10. A method for manufacturing a semiconductor device comprising a
step of polishing an inorganic insulating film having unevenness on
a surface thereof, to be polished, by moving a substrate on which
the film to be polished is formed and a polishing platen while
pressing the substrate against the polishing platen and a polishing
cloth and supplying said CMP abrasive for polishing an inorganic
insulating film having unevenness on a surface thereof according to
claim 1, between the inorganic insulating film to be polished and
the polishing cloth.
11. The CMP abrasive according to claim 1, wherein said dispersant
is selected from the group consisting of water-soluble anionic
dispersants, water-soluble nonionic dispersants, water-soluble
cationic dispersants and water-soluble amphoteric dispersants.
12. The CMP abrasive according to claim 1, wherein said organic
polymer is included in an amount of 0.01 part by weight to 100
parts by weight, based on 100 parts by weight of cerium oxide
particles.
13. The CMP abrasive according to claim 1, consisting of the cerium
oxide particles, the dispersant, water and the organic polymer.
14. The CMP abrasive according to claim 1, wherein the cerium oxide
particles have an average particle diameter of 0.01 .mu.m to 1.0
.mu.m.
15. The CMP abrasive according to claim 1, wherein said organic
polymer is selected from the group consisting of poly (meth)
acrylic acid ammonium salts.
16. The CMP abrasive according to claim 1, wherein said organic
polymer is selected from the group consisting of poly (meth)
acrylic acid derivatives.
17. The CMP abrasive according to claim 1, wherein said CMP
abrasive is adapted to polish an oxide insulating film having
unevenness on a surface thereof.
18. The CMP abrasive according to claim 17, wherein said CMP
abrasive is adapted to polish a silicon oxide insulating film
having unevenness on a surface thereof.
19. The CMP abrasive according to claim 1, wherein said CMP
abrasive is adapted to polish a silicon oxide film having
unevenness on a surface thereof.
Description
TECHNICAL FIELD
The present invention relates to a CMP (Chemical Mechanical
Polishing) abrasive used in a step for smoothing a surface of a
substrate, particularly in a step for smoothing an interlayer
insulating film and a BPSG (a boron phosphorus-doped silicon
dioxide film) film, a step for forming shallow trench isolation or
the like which are semiconductor element manufacturing techniques,
a method for polishing a substrate and a method for manufacturing a
semiconductor device using this CMP abrasive, and an additive for a
CMP abrasive.
BACKGROUND ART
Current ultra large scale integrated circuits tend to enhance
packaging density, and various microscopic processing technologies
have been studied and developed. Thus, the design-rule has reached
a sub half micron order. One of the technologies which have been
developed to satisfy requirements for such severe fining is a CMP
technology. This CMP technology can fully smooth a layer to be
exposed, reduce the load of an exposure technology, and stabilize
the yield in steps for manufacturing semi-conductor devices. Thus,
the CMP technology is an essential technology for smoothing an
interlayer insulating film and a BPSG film, and performing shallow
trench isolation, for example.
In steps for manufacturing semiconductor devices, as a CMP abrasive
for smoothing inorganic insulating films such as silicon oxide
insulating films formed by a plasma-CVD (Chemical Vapor Deposition)
method, a low pressure-CVD method or the like, fumed silica series
abrasives have been generally studied. The fumed silica series
abrasives are produced by causing grain growth by a process of
subjecting to pyrolysis of silica particles into silicic
tetrachloride or the like and by performing pH adjustment. However,
such an abrasive incurs technical problems that the polishing speed
for inorganic insulating films is not sufficient, causing a low
polishing speed in practical use.
In a conventional CMP technology for smoothing an interlayer
insulating film, there are technical problems that high level
smoothing cannot be realized in the entire surface of a wafer since
the dependency of polishing speed on the pattern of a film to be
polished on a substrate is great, the polishing speeds in projected
portions are largely differentiated due to the magnitude of the
pattern density difference or the size difference, and the
polishing of even recessed portions proceeds.
Further, in the CMP technology for smoothing the interlayer film,
it is necessary to finish polishing in the middle of the interlayer
film, and a method for controlling a process of controlling the
amount of polishing by polishing time has been generally carried
out. However, since the polishing speed is remarkably changed not
only due to the change in shapes of pattern steps, but also due to
the conditions of polishing cloth and the like, there is the
problem that process management is difficult.
LOCOS (Local Oxidation of Silicon) had been used for element
isolation in integrated circuits in the generation of a 0.5 .mu.m
or more design-rule. As the working size becomes finer thereafter,
technologies of narrower width of element isolation have been
required and shallow trench isolation is being used. In the shallow
trench isolation, the CMP is used for removing excess silicon oxide
films formed on a substrate and a stopper film having a slow
polishing speed is formed beneath the silicon oxide film to stop
the polishing. As a stopper film, silicon nitride and the like are
used, and preferably, the ratio of the polishing speed between the
silicon oxide film and the stopper film is large. Conventional
fumed silica series abrasives have a polishing speed ratio of as
small as about 3 between the above-mentioned silicon oxide film and
the stopper film, and the fumed silica abrasives have a problem
that they do not have properties endurable for practical use for
shallow trench isolation.
On the other hand, as the glass-surface abrasive for photomasks,
lenses, and the like, a cerium oxide abrasive has been used. As
cerium oxide particles have lower hardness than silica particles or
alumina particles, they tend to cause few scratches on a surface to
be polished so that they are useful for finishing mirror polishing.
However, since the cerium oxide abrasive for glass surface
polishing uses a dispersant containing a sodium salt, it cannot be
applied to an abrasive for semiconductors as it is.
An object of the present invention is to provide a CMP abrasive
which is capable of polishing a surface to be polished such as a
silicon oxide insulating film at high speed without causing
scratches while attaining high level smoothing and has a high
storage stability.
Another object of the present invention is to provide a method for
polishing a substrate which is capable of polishing a surface to be
polished of a substrate at high speed without causing scratches
while attaining high level smoothing with easy process control.
A further object of the present invention is to provide a method
for manufacturing a semiconductor device which is capable of
manufacturing a semiconductor device having a high reliability with
high productivity and good yield. A still further object of the
present invention is to provide an additive for a CMP abrasive,
which CMP abrasive is capable of polishing a surface to be polished
at high speed without causing scratches while attaining high level
smoothing, and particularly capable of providing the CMP abrasive
with an excellent storage stability.
DISCLOSURE OF THE INVENTION
The present invention relates to a CMP abrasive comprising cerium
oxide particles, a dispersant, an organic polymer having an atom or
a structure capable of forming a hydrogen bond with a hydroxyl
group present on a surface of the film to be polished, and
water.
Further, the present invention relates to the CMP abrasive in which
the organic polymer is a compound containing at least one atom
having an unpaired electron in the molecular structure.
Further, the present invention relates to the CMP abrasive in which
the organic polymer is a compound containing either one or both of
a nitrogen atom and an oxygen atom in the molecular structure.
Further, the present invention relates to the CMP abrasive in which
the organic polymer is a compound having an adsorption ratio of 50%
or more with respect to silicon oxide particles of a specific
surface area of 50 m.sup.2/g dispersed in water of pH 6 to 8.
Further, the present invention relates to the CMP abrasive in which
the organic polymer is a compound having an adsorption ratio of 40%
or more with respect to silicon nitride particles of a specific
surface area of 3.3 m.sup.2/g dispersed in water of pH 6 to 8.
Further, the present invention relates to the CMP abrasive in which
the sedimentation speed for cerium oxide particles is 20 .mu.m/s or
less.
The present invention also relates to the CMP abrasive in which the
organic polymer is polyvinyl pyrrolidone.
Further, the present invention relates to a method for polishing a
substrate comprising polishing a film to be polished by moving a
substrate on which the film to be polished was formed and a
polishing platen while pressing the substrate against the polishing
platen and a polishing cloth and supplying the CMP abrasive between
the film to be polished and the polishing cloth.
Further, the present invention relates to a method for
manufacturing a semiconductor device comprising a step of polishing
a film to be polished by moving a substrate on which the film to be
polished is formed and a polishing platen while pressing the
substrate against the polishing platen and a polishing cloth and
supplying the CMP abrasive between the film to be polished and the
polishing cloth.
Further, the present invention relates to an additive for a CMP
abrasive comprising an organic polymer having an atom or a
structure capable of forming a hydrogen bond with a hydroxyl group
present on a surface of a film to be polished, and water.
BEST MODE FOR CARRYING OUT THE INVENTION
Cerium oxide particles in the present invention are obtained by
oxidizing cerium salts such as carbonate of cerium, nitrate of
cerium, sulfate of cerium and oxalate of cerium. The cerium oxide
particles preferably have a crystalline diameter of 5 to 300 nm
from the viewpoints of high speed polishing and low scratch
properties.
In the present invention, as methods for preparing cerium oxide,
calcination or an oxidation method of using hydrogen peroxide,
etc., can be used. Preferably, the calcining temperature is
350.degree. C. or higher and 900.degree. C. or lower.
Since the cerium oxide particles manufactured by the above method
are agglomerated, it is preferred to mechanically grind them. The
grinding methods preferably include a dry grinding method with a
jet mill or the like and a wet grinding method with a planetary
bead mill or the like. The jet mill is described in, for example,
the Chemical Industry Theses, Vol. 6, No. 5 (1980) pp. 527 to
532.
The CMP abrasive according to the present invention can be
manufactured by first preparing a dispersion of cerium oxide
particles (hereinafter sometimes referred to as a "slurry")
comprising cerium oxide particles, a dispersant and water, and
adding an organic polymer having an atom or a structure capable of
forming a hydrogen bond with a hydroxyl group present on a surface
of a film to be polished (hereinafter sometimes referred to as
merely "organic polymer") therein. Here, the concentration of the
cerium oxide particles is not limited, but it is preferably in the
range of from 0.5 to 20% by weight from the viewpoint of handling
of the dispersion.
As the dispersants, there may be mentioned a water-soluble anionic
dispersant, a water-soluble nonionic dispersant, a water-soluble
cationic dispersant, and a water-soluble amphoteric dispersant.
As the above-mentioned water-soluble anionic dispersants, there may
be mentioned, for example, lauryl sulfate triethanolamine, lauryl
sulfate ammonium, polyoxyethylene alkyl ether sulfate
triethanolamine and polycarboxylic acid series polymer (for
example, an alkali metal salt or ammonium salt of a (co) polymer
comprising (meth)acrylic acid, alkyl (meth)acrylate used depending
on necessity and vinyl monomer used depending on necessity). Here,
the (meth)acrylic acid in the present invention means an acrylic
acid and a methacrylic acid corresponding thereto, and the alkyl
(meth)acrylate means an alkyl acrylate and an alkyl methacrylate
corresponding thereto.
As the above-mentioned water-soluble nonionic dispersants, there
may be mentioned, for example, polyoxyethylene lauryl ether,
polyoxyethylene cetyl ether, polyoxyethylene stearyl ether,
polyoxyethylene oleyl ether, polyoxyethylene higher alcohol ether,
polyoxyethylene octyl phenyl ether, polyoxyethylene nonyl phenyl
ether, polyoxyalkylene alkyl ether, polyoxyethylene derivative,
polyoxy-ethylene sorbitan monolaurate, polyoxyethylene sorbitan
monopalmitate, polyoxyethylene sorbitan monostearate,
polyoxyethylene sorbitan tristearate, polyoxyethylene sorbitan
monooleate, polyoxyethylene sorbitan trioleate, tetraoleic acid
polyoxyethylene sorbitol, polyethylene glycol monolaurate,
polyethylene glycol monostearate, polyethylene glycol distearate,
polyethylene glycol monooleate, polyoxyethylene alkylamine,
polyoxyethylene hardened castor oil, and alkyl alkanolamide,
etc.
As the above-mentioned water-soluble cationic dispersants, there
may be mentioned, for example, coconut amine acetate and
stearylamine acetate, etc.
Further, as the above-mentioned water-soluble amphoteric
dispersants, there may be mentioned, for example, lauryl betaine,
stearyl betaine, lauryldimethyl amine oxide, and
2-alkyl-N-carboxymethyl-N-hydroxyethyl imidazolinium betaine,
etc.
It is preferred that the amount of these dispersants to be added is
in the range of 0.01 part by weight or more and 2.0 parts by weight
or less based on 100 parts by weight of cerium oxide particles from
the viewpoint of improvement of dispersibility or prevention of
sedimentation of cerium oxide particles in a slurry, and prevention
of polishing scratches, and the like. The weight average molecular
weight (a value obtained by measuring with GPC and calculated in
terms of standard polystyrene) is preferably 100 to 50,000, more
preferably 1,000 to 10,000. When the molecular weight of the
dispersant is less than 100, sufficient polishing speed cannot be
obtained in polishing a silicon oxide film or a silicon nitride
film, and when the molecular weight of the dispersant exceeds
50,000, the viscosity thereof becomes high and the storage
stability of a CMP abrasive tends to be lowered.
In the methods of dispersing these cerium oxide particles into
water, in addition to the dispersion processing using a usual
stirrer, a homogenizer, an ultrasonic dispersing machine, a wet
type ball mill and the like can be used.
The average particle diameter of the thus prepared cerium oxide
particles in a slurry is preferably 0.01 .mu.m to 1.0 .mu.m. When
the average particle diameter of the cerium oxide particles is less
than 0.01 .mu.m, the polishing speed tends to become low, and when
the average particle diameter thereof exceeds 1.0 .mu.m, the
abrasive tends to cause scratches on a film to be polished.
Although organic polymers having an atom or a structure capable of
forming a hydrogen bond with a hydroxyl group present on a surface
of a film to be polished are not particularly limited as long as
they have a defined particular atom or structure, there may be
mentioned, for example, a compound containing at least one atom
having an unpaired electron in the molecular-structure, or a
compound containing either one or both of a nitrogen atom and an
oxygen atom in the molecular structure.
Specifically, there may be mentioned polyvinyl acetal, polyvinyl
formal, polyvinyl butyral, polyvinyl pyrrolidone, polyvinyl
pyrrolidone-iodine complex, polyvinyl (5-methyl-2-pyrrolidinone),
polyvinyl (2-piperidinone), polyvinyl
(3,3,5-trimethyl-2-pyrrolidinone), poly(N-vinylcarbazole),
poly(N-alkyl-2-vinylcarbazole), poly(N-alkyl-3-vinyl-carbazole),
poly(N-alkyl-4-vinylcarbazole), poly(N-vinyl-3,6-dibromocarbazole),
polyvinyl phenyl ketone, polyvinyl acetophenone,
poly(4-vinylpyridine), poly(4-.beta.-hydroxy-ethylpyridine),
poly(2-vinylpyridine), poly(2-.beta.-hydroxy-ethylpyridine,
poly(4-vinylpyridinium salt),
poly(.alpha.-methyl-styrene-co-4-vinyl pyridinium hydrochloride),
poly-(potassium 1-(3-sulfonyl)-2-vinylpyridinium
betaine-co-p-styrene sulfonate), poly(N-vinylimidazole),
poly(4-vinyl imidazole), poly(5-vinyl imidazole),
poly(1-vinyl-4-methyl-oxazolidinone), polyvinyl acetamide,
polyvinyl methyl acetamide, polyvinyl ethyl acetamide, polyvinyl
phenyl acetamide, polyvinyl methyl propionamide, polyvinyl ethyl
propionamide, polyvinyl methyl isobutylamide, polyvinyl methyl
benzylamide, poly(meth)acrylic acid, poly(meth)-acrylic acid
derivatives, poly(meth)acrylic acid ammonium salts, polyvinyl
alcohol, polyvinyl alcohol derivatives, polyacrolein,
polyacrylonitrile, polyvinyl acetate, poly(vinyl acetate-co-methyl
methacrylate), poly(vinyl acetate-co-vinyl acrylate), poly(vinyl
acetate-co-pyrrolidine), poly(vinyl acetate-co-acetonitrile),
poly(vinyl acetate-co-N,N-diallyl cyanide), poly(vinyl
acetate-co-N,N-diallyl amine), and poly(vinyl acetate-co-ethylene),
etc. Among these polymers, polyvinyl pyrroli-done,
poly(meth)acrylic acid derivative, and poly(meth)-acrylic acid
ammonium salts are preferable, and polyvinyl pyrrolidone is
particularly preferable.
The organic polymer is preferably a compound having an adsorption
ratio of 50% or more with respect to silicon oxide particles
dispersed in water of pH 6 to 8 and having a specific surface area
of 50 m.sup.2/g, from the viewpoint of performing excellent
polishing for shallow trench isola-tion. Further, from the same
viewpoint, it is preferably a compound having an adsorption ratio
of 40% or more to silicon nitride particles having a specific
surface area of 3.3 m.sup.2/g dispersed in water of pH 6 to 8.
The amount of these organic polymers to be added is preferably in a
range of 0.01 part by weight to 100 parts by weight, more
preferably 0.1 part by weight to 50 parts by weight, and most
preferably 1 part by weight to 50 parts by weight, based on 100
parts by weight of cerium oxide particles from the viewpoint of
improvement in dispersibility of the cerium oxide particles in CMP
abrasive, prevention of sedimentation and prevention of polishing
scratches. Further, the weight average molecular weight of the
organic polymer (a value obtained by measuring with a GPC and
calculated in terms of standard polystyrene) is preferably 5,000 to
2,000,000, and more preferably 10,000 to 1, 200,000.
In the present invention, a cerium oxide slurry comprising cerium
oxide particles, a dispersant, and water, and an additive for a CMP
abrasive comprising an organic polymer and water may be divided,
and may be stored and utilized as a two-liquid type CMP
abrasive.
When a substrate is polished by the above-mentioned CMP abrasive,
there can be employed a method having steps of separately supplying
the slurry and additive onto a polishing platen, and mixing them
thereon, a method having steps of mixing the slurry and additive
just before polishing and supplying the mixture onto a polishing
platen, etc.
To the CMP abrasive according to the present invention, additives
such as N,N-dimethylethanolamine, N,N-diethylethanolamine,
aminoethylethanolamine and the like may be added.
In the CMP abrasive of the present invention, the sedimentation
speed of the cerium oxide particles is preferably 20 .mu.m/s or
less from the viewpoint of workability.
An inorganic insulating film which is one of films to be polished
using a CMP abrasive of the present invention is formed by a
low-pressure CVD method, a plasma CVD method or the like.
Formation of a silicon oxide film by the low-pressure CVD method
uses monosilane: SiH.sub.4 as an Si source, and oxygen: O.sub.2 as
an oxygen source. A silicon oxide film can be obtained by
performing this SiH.sub.4--O.sub.2 series oxidation reaction at a
low temperature of 400.degree. C. or lower. Heat treatment is
optionally performed at a temperature of 1,000.degree. C. or lower
after the CVD process. When phosphorus: P is doped to attain the
surface smoothness by a high-temperature reflow process, an
SiH.sub.4--O.sub.2--PH.sub.3 series reaction gas is preferably
used.
The plasma CVD method has such an advantage that a chemical
reaction, which requires a high temperature under usual thermal
equilibrium, can be performed at a low temperature. The plasma
generation method includes two types: a volume connection type and
an induction connection type. The reaction gases include an
SiH.sub.4--N.sub.2O series gas using SiH.sub.4 as an Si source and
N.sub.2O as an oxygen source, and TEOS-O.sub.2 series gas
(TEOS-plasma CVD method) using tetra-ethoxysilane (TEOS) as an Si
source. The temperature of a substrate is preferably in a range of
250.degree. C. to 400.degree. C., and the reaction pressure is
preferably in a range of 67 to 400 Pa. Thus, to the silicon oxide
film of the present invention, elements such as phosphorus and
boron may be doped.
Similarly, formation of silicon nitride film by the low-pressure
CVD method uses dichlorosilane: SiH.sub.2Cl.sub.2 as an Si source
and ammonia: NH.sub.3 as a nitrogen source. A silicon nitride film
can be obtained by performing this SiH.sub.2Cl.sub.2--NH.sub.3
series oxidation reaction at a high temperature of 900.degree.
C.
In the plasma CVD method, the reaction gases include an
SiH.sub.4--NH.sub.3 series gas using SiH.sub.4 as an Si source and
NH.sub.3 as a nitrogen source. The temperature of a substrate is
preferably 300.degree. C. to 400.degree. C.
As a substrate, a semiconductor substrate, that is a semiconductor
substrate in a phase of circuit elements and a wiring pattern
formed thereon, or circuit elements formed thereon and the like on
which a silicon oxide film layer or a silicon nitride film layer is
formed can be used. By polishing the silicon oxide film or silicon
nitride film formed on such a semiconductor substrate with a CMP
abrasive, the projections and recessions of a surface of the
silicon oxide film layer are removed and a smooth surface over the
entire surface of the semiconductor substrate can be obtained.
Further, it can be also used for shallow trench isolation. To use
it for shallow trench isolation, the ratio between the silicon
oxide film polishing speed and the silicon nitride film polishing
speed, that is the silicon oxide film polishing speed/the silicon
nitride film polishing speed is preferably 10 or more. In the case
where this ratio is less than 10, the difference between the
silicon oxide film polishing speed and the silicon nitride film
polishing speed is small, and stopping the polishing at a
predetermined position tends to become difficult in the shallow
trench isolation. In the case where this ratio is 10 or more, the
silicon nitride film polishing speed is further reduced, rendering
stoppage of polishing easy, thus making it more suitable for
shallow trench isolation.
To use the CMP abrasive for the shallow trench isolation, it is
preferred that generation of scratches during polishing be
small.
Here, as a polishing device, a general polishing device having a
holder which supports a semiconductor substrate, and a platen to
which a polishing cloth (pad) is adhered (a motor whose number of
revolutions is changeable is attached) can be used.
As a polishing cloth, a general nonwoven fabric, an expanded
polyurethane, a porous fluorine resin or the like can be used
without specific limitation. Further, it is preferred that a groove
in which the CMP abrasive is stored be formed in the polishing
cloth.
Although the polishing conditions are not limited, the rotational
speed of the platen is preferably low as 200 min.sup.-1 or less so
that the semiconductor substrate does not come off, and the
pressure applied to the semiconductor substrate is preferably
10.sup.5 Pa or less so that no scratches will be present after
polishing.
During polishing, a slurry is continuously supplied onto a
polishing cloth with a pump or the like. Although the amount of a
slurry supplied is not limited, it is preferred that the surface of
the polishing cloth be always covered with a slurry.
It is preferred that after the polished semiconductor substrate is
washed well in running water, water drops attached onto the
semiconductor substrate be shaken off with a spin dryer or the like
and dried.
Thus, after the smoothed shallow trench is formed, an aluminum
wiring is formed on a silicon oxide insulating film layer, and a
silicon oxide insulating film is formed between the wirings and on
the wiring by the above-mentioned process again, then polishing is
performed using the CMP abrasive so that the projections and
recessions on a surface of the insulating film are removed to form
a smooth surface over the entire surface of the semiconductor
substrate. By repeating these steps for predetermined times, a
semiconductor having a desired number of layers is
manufactured.
The CMP abrasive according to the present invention can polish not
only a silicon oxide film formed on a semiconductor substrate, but
also a silicon oxide film formed on a wiring board having
predetermined wiring, an inorganic insulating film such as glass,
silicon nitride, etc., a film principally containing polysilicon,
Al, Cu, Ti, TiN, W, Ta, TaN and the like, an optical glass such as
a photomask, a lens, and a prism, an inorganic conducting film such
as ITO, an optical integrated circuit, an optical switching
element, an optical waveguide constituted by glass and a
crystalline material, an end surface of optical fiber, an optical
single crystal such as a scintillator, a solid laser single
crystal, a sapphire substrate for a blue laser LED, a semiconductor
single crystal such as SiC, GaP and GaAs, a glass substrate for a
magnetic disk, a magnetic head and the like.
EXAMPLE
The present invention will be described below in detail using
Examples, but the present invention is not limited thereto.
Example 1
Preparation of Cerium Oxide Particles
2 kg of a cerium carbonate hydrate was placed into a vessel made of
alumina, and calcined at a temperature of 800.degree. C. for 2
hours in the air to obtain about 1 kg of yellowish white powder.
This powder was phase-identified by the X-ray diffractometry
whereby it was confirmed to be cerium oxide. The diameter of the
calcined powder particles was 30 to 100 .mu.m. The surface of the
calcined powder particle was observed with a scanning type electron
microscope, and then particle boundaries of the cerium oxide were
observed. A primary particle diameter of a cerium oxide surrounded
by the grain boundary was measured. The median value and the
maximum value in the volume distribution were 190 nm and 500 nm,
respectively.
1 kg of cerium oxide powder was dry-ground with a jet mill. The
observation of the ground particles was performed with a scanning
type electron microscope. As a result, not only small particles
having the same size as the primary particle diameter, but also
remaining not-ground large particles of 1 to 3 .mu.m and remaining
not-ground particles of 0.5 to 1 .mu.m were found to be mixed with
each other.
(Measurement of Adsorption of Organic Polymer to Silicon Oxide
Particles)
100 g of a testing water having a concentration of 500 ppm
polyvinyl pyrrolidone with a weight average molecular weight of
25,000 was adjusted to pH 7.0, and 50 g of the testing water was
measured and taken out. Then, 0.5 g of silicon oxide particles
having a specific surface area of 50 m.sup.2/g were added to the
water and shaken reciprocally for 10 minutes. After that,
centrifugal separation was conducted at 15,000 min.sup.-1, for 5
minutes to obtain a supernatant liquid. Subsequently, the total
amount of organic carbon (TOC) in this supernatant (liquid A) and
that of the remaining testing water (liquid B) not mixed with
silicon oxide particles were measured respectively with a total
organic carbon meter TOC-5000 manufactured by Shimadzu Corp. The
measurement of TOC was determined by subtracting the amount of the
inorganic carbon (IC) from the total amount of carbon (TC).
Further, silica particles were similarly mixed with pure water and
shaken, and after centrifugal separation, the TOC value of the
supernatant was set to a blank value. The TOC values of the liquids
A and B were defined as TOCA and TOCB, respectively, and the
adsorbed amount was calculated by the expression of
(TOCB-TOCA/TOCA). As a result, the adsorbed amount of
polypyrrolidone to the silicon oxide particles was 78%.
(Adsorption of Organic Polymer to Silicon Nitride Particles)
100 g of testing water having a concentration of 50 ppm polyvinyl
pyrrolidone with a weight average molecular weight of 25,000 was
adjusted to pH 7.0, and 50 g of the testing water was measured and
taken out. Then, 4 g of silicon oxide particles having a specific
surface area of 3.3 m.sup.2/g were added to the water and shaken
reciprocally for 10 minutes. After that, centrifugal separation was
conducted at 15,000 min.sup.-1 for 5 minutes to obtain a
supernatant. Subsequently, the total amount of organic carbon (TOC)
in the supernatant (liquid C) and that of the remaining testing
water (liquid D) not mixed with silicon oxide particles were
measured, respectively, with a total organic carbon meter TOC-5000
manufactured by Shimadzu Corp. The measurement of TOC was
determined by subtracting the amount of inorganic carbon (IC) from
the total amount of carbon (TC).
Further, silica particles were similarly mixed with pure water and
shaken, and after centrifugal separation, the TOC value of the
supernatant was set to a blank value. The TOC values of the liquids
C and D were defined as TOCC and TOCD respectively, and the
adsorbed amount was calculated by an expression of
(TOCD-TOCC/TOCD). As a result, the adsorbed amount of polyvinyl
pyrrolidone to the silicon oxide particles was 53%.
(Preparation of Cerium Oxide Slurry)
1 kg of the above-prepared cerium oxide particles, 23 g of an
aqueous ammonium polyacrylate solution (40% by weight) and 8,977 g
of deionized water were mixed and ultrasonic dispersion was
performed for 10 minutes while stirring. The obtained slurry was
filtered with a 1 micron filter, and a slurry (solid content: 5% by
weight) was obtained by further adding deionized water. The pH of
this slurry was 8.3. To measure the slurry particles with a laser
diffraction type grain size distribution meter, the particles were
diluted to an appropriate concentration. As a result, the median
value of the particle diameters was 190 nm.
Further, 600 g of the cerium oxide slurry (solid content: 5% by
weight), 3 g of polyvinyl pyrrolidone with a weight average
molecular weight of 25,000 as an additive and 2,397 g of deionized
water were mixed to prepare a CMP abrasive (solid content: 1% by
weight). The pH of this CMP abrasive was 8.0. To measure the
particles in the CMP abrasive with a laser diffraction type grain
size distribution meter, the particles were diluted to an
appropriate concentration. As a result, the median value of the
particle diameters was 190 nm.
(Measurement of Sedimentation Speed)
500 g of the cerium oxide slurry prepared in the above section
"preparation of cerium oxide slurry" was placed into an Andreasen
pippette and left to stand. Immediately after the operation, 10 ml
of slurry was sampled from a position of 20 cm below the surface of
the cerium oxide slurry, and the concentration thereof was
measured.
The same operation was performed after 3 hours, 6 hours, 24 hours,
2 days, 5 days, 8 days, 13 days, 20 days, 30 days, 70 days and 120
days.
As a result, the average sedimentation speed of the cerium oxide
slurry was 0.11 .mu.m/s.
Here, the average sedimentation speed means a value obtained by
dividing 20 cm by the time required for the concentration measured
in the above-mentioned manner to reduce into the half of the
initial 5% by weight, or 2.5% by weight.
The time required at this time was 21 days. Further, a
concentration measured after 6 days was 5% by weight, which was not
changed. Thus, the maximum sedimentation speed of this cerium oxide
slurry is 9 .mu.m/s or less. That is, the sedimentation speed of
all the cerium oxide particles contained in this cerium oxide
slurry is 9 .mu.m/s or less.
(Polishing of Insulating Film Layer)
After an Al wiring line portion having a line/space width of 0.05
to 5 mm and a height of 1,000 nm was formed on an Si substrate
having a diameter of 200 mm, a pattern wafer on which a 2,000 nm
thick silicon oxide film was formed by the TEOS-plasma CVD method
was prepared.
The above-mentioned pattern wafer was set on a holder to which an
adsorption pad for mounting a substrate to be held was adhered, and
the holder was placed on a platen having a diameter of 600 mm, to
which a polishing pad made of a porous urethane resin was adhered
with the insulating film surface down, and then the working load
was set to 30 kPa.
The platen and the wafer were rotated for 2 minutes at a rotational
speed of 50 min.sup.-1 while dropping the above-mentioned cerium
oxide abrasive (solid content: 1% by weight) on the platen at a
dropping speed of 200 ml/min, thereby polishing the insulating
film.
After the polished wafer was washed well with pure water, it was
dried. Similarly, the above-mentioned pattern wafers were polished
for polishing-time of 3 minutes, 4 minutes, 5 minutes and 6
minutes.
Using an optical interference type film thickness measuring device,
the thickness difference before and after polishing were measured
and the polishing speed was calculated.
Polishing speed of a line portion having a line/space width of 1 mm
is defined as R.sub.1, the polishing speed of a line portion having
a line/space width of 3 mm as R.sub.3, and the polishing speed of a
line portion having a line/space width of 5 mm as R.sub.5. The
polishing speed ratios R.sub.5/R.sub.1 and R.sub.3/R.sub.1 became
larger for polishing time between polishing time of 2 and 4 minutes
according to the increase in the polishing time, and became
substantially constant between polishing time of 4 and 6
minutes.
In the case of 4 minutes polishing time where the pattern width
dependency of the polishing speed becomes constant, the polishing
speed R.sub.1 for a line portion having a line/space width of 1 mm
was 344 nm/min (amount of polishing: 1,377 nm), the polishing speed
R.sub.3 for a line portion having a line/space width of 3 mm was
335 nm/min (amount of polishing: 1,338 nm), and the polishing speed
R.sub.5 for a line portion having a line/space width of 5 mm was
315 nm/min (amount of polishing: 1,259 nm), and the polishing speed
ratios R.sub.5/R.sub.1 and R.sub.3/R.sub.1 were 0.91 and 0.97,
respectively.
The amounts of polishing of line portions in each line/space width
for the polishing time of 5 minutes and 6 minutes were
substantially the same as in the case of 4 minutes, and it was
found that no polishing advanced at all after 4 minutes.
Example 2
Preparation of Cerium Oxide Particles
2 kg of cerium carbonate hydrate was placed into a vessel made of
platinum, and calcined at a temperature of 800.degree. C. for 2
hours in the air to obtain about 1 kg of yellowish white powder.
This powder was phase-identified by the X-ray diffractometry,
whereby the powder was confirmed to be cerium oxide. The diameters
of the calcined powder particles were 30 to 100 .mu.m. The surface
of the calcined powder particles was observed with a scanning type
electron microscope, and particle boundaries of the cerium oxide
were observed. A primary particle diameter of a cerium oxide
particle surrounded by the grain boundary was measured. The median
value and the maximum value in the volume distribution were 190 nm
and 500 nm, respectively.
1 kg of cerium oxide powder was dry-ground with a jet mill. The
observation of the ground particles was performed with a scanning
type electron microscope. As a result, not only small particles
having the same size as the primary particle diameter, but also
remaining not-ground large particles of 1 to 3 .mu.m and remaining
not-ground particles of 0.5 to 1 .mu.m were found to be mixed with
each other.
(Preparation of Cerium Oxide Slurry)
1 kg of the prepared cerium oxide particles, 23 g of an aqueous
ammonium polyacrylate solution (40% by weight) and 8,977 g of
deionized water were mixed and ultrasonic dispersion was performed
for 10 minutes while stirring. The obtained slurry was filtered
with a 1 micron filter, and a slurry (solid content: 5% by weight)
was obtained by adding deionized water. The pH of this slurry was
8.3. To measure the slurry particles with a laser diffraction type
grain size distribution meter, the particles were diluted to an
appropriate concentration. As a result, the median value of the
particle diameters was 190 nm.
Further, 600 g of the cerium oxide slurry (solid content: 5% by
weight), 3 g of polyvinyl pyrrolidone as an additive and 2,397 g of
deionized water were mixed to prepare a CMP abrasive (solid
content: 1% by weight). The pH of this CMP abrasive was 8.0. To
measure the particles in the CMP abrasive with a laser diffraction
type grain size distribution meter, the particles were diluted to
an appropriate concentration. As a result, the median value of the
particle diameters was 190 nm.
(Polishing of Shallow Trench Separation Layer)
Projected portions each having a square section of a side of 350 nm
to 0.1 mm and recessed portions each having a depth of 400 nm were
formed on an Si substrate having a diameter of 200 mm, and a
pattern wafer having the projected portion density of 2 to 40% was
prepared.
A 100 nm thick nitrogen oxide film was formed on the projected
portions and a 500 nm thick silicon oxide film was formed thereon
by the TEOS-plasma CVD method.
The above-mentioned pattern wafer was set on a holder to which an
adsorption pad for mounting a substrate to be held was adhered, and
the holder was placed on a platen having a diameter of 600 mm to
which a polishing pad made of a porous urethane resin was adhered
with the insulating film surface down, and further the working load
was set to 30 kPa.
The platen and the wafer were rotated for 4 minutes at a rotational
speed of 50 min.sup.-1 while dropping the above-mentioned CMP
abrasive (solid content: 1% by weight) on the platen at a dropping
speed of 200 ml/min, thereby polishing the insulating film. After
the polished wafer was washed well with pure water, it was dried.
Similarly, the above-mentioned pattern wafers were polished by
setting the polishing time to 5 minutes and 6 minutes.
Using an optical interference type film thickness measuring device,
the film thicknesses before and after polishing were measured. At
the polishing time of 4 minutes, the entire silicon oxide film on
the projected portions was polished, and when the nitrogen oxide
film was exposed, the polishing stopped. Then the film thickness
before and after polishing was measured and the polishing speed was
calculated. The polishing speeds on projected portions having 0.1
mm square and densities of 40% and 2% are defined as R.sub.0.1-40
and R.sub.0.1-2, respectively, and the polishing speeds on
projected portions having 350 nm square and densities of 40% and 2%
are defined as R.sub.350-40 and R.sub.350-2, respectively. In the
case where polishing time was set to 4 minutes, R.sub.0.1-40,
R.sub.0.1-2, R.sub.350-40 and R.sub.350-2 were 126 nm/min, 135
nm/min, 133 nm/min, and 137 nm/min, and R.sub.0.1-40/R.sub.350-40
and R.sub.0.1-2/R.sub.350-2 were 0.95 and 0.99, respectively. Thus,
there was no pattern width dependency. Further, the amounts of
polishing in the projected portions in each pattern width in the
case of polishing time of 5 minutes and 6 minutes were
substantially the same as in the case of 4 minutes, and it was
found that no polishing advanced at all after 4 minutes.
Comparative Example 1
Preparation of Cerium Oxide Particles
2 kg of cerium carbonate hydrate was placed into a vessel made of
platinum, and calcined at a temperature of 800.degree. C. for 2
hours in the air to obtain about 1 kg of yellowish white powder.
This powder was phase-identified by an X-ray diffractometry,
whereby the powder was confirmed to be cerium oxide. The diameter
of the calcined powder particle was 30 to 100 .mu.m. A surface of
the calcined powder particle was observed with a scanning type
electron microscope, and particle boundaries in the cerium oxide
were observed. A primary particle diameter of a cerium oxide
surrounded by the grain boundary was measured. The median value and
the maximum value in the volume distribution were 190 nm and 500
nm, respectively.
1 kg of cerium oxide powder was dry-ground with a jet mill. The
observation of the ground particles was performed with a scanning
type electron microscope. As a result, not only small particles
having the same size as the primary particle diameter, but also
remaining not-ground large particles of 1 to 3 .mu.m and remaining
not-ground particles of 0.5 to 1 .mu.m were found to be mixed with
each other.
(Preparation of Cerium Oxide Slurry)
1 kg of the prepared cerium oxide particles, 23 g of an aqueous
ammonium polyacrylate solution (40% by weight) and 8,977 g of
deionized water were mixed and ultrasonic dispersion was performed
for 10 minutes while stirring. The obtained slurry was filtered
with a 1 micron filter, and a cerium oxide slurry (solid content:
5% by weight) was obtained by further adding deionized water. The
pH of this cerium oxide slurry was 8.3.
600 g of the above-mentioned cerium oxide slurry (solid content: 5%
by weight), and 2,400 g of deionized water were mixed to prepare an
abrasive (solid content: 1% by weight). The pH of this abrasive was
7.4. To measure the particles in the abrasive with a laser
diffraction type grain size distribution meter, the particles were
diluted to an appropriate concentration. As a result, the median
value of the particle diameters was 190 nm.
(Polishing of Insulating Film)
After an Al wiring line portion having a line/space width of 0.05
to 5 mm and a height of 1,000 nm was formed 3H on an Si substrate
having a diameter of 200 mm, a pattern wafer on which a 2,000 nm
thick silicon oxide film was formed by the TEOS-plasma CVD method
was prepared.
The pattern wafer was set on a holder to which an adsorption pad
for mounting a substrate to be held was adhered, and the holder was
placed on a platen having a diameter of 600 mm to which a polishing
pad made of a porous urethane resin was adhered with the insulating
film surface down, and then the working load was set to 30 kPa.
The platen and the wafer were rotated for 1 minute at a rotational
speed of 50 min.sup.-1 while dropping the above-mentioned cerium
oxide slurry (solid content: 1% by weight) on the platen at a
dropping speed of 200 ml/min, thereby polishing the insulating
film. After the polished wafer was washed well with pure water, it
was dried. Similarly, the above-mentioned pattern wafers were
polished by setting the polishing times to 1.5 minutes and 2
minutes.
Polishing speed of a line portion having a line/space width of 1 mm
is defined as R.sub.1, the polishing speed of a line portion having
a line/space width of 3 mm as R.sub.3, and the polishing speed of a
line portion having a line/space width of 5 mm as R.sub.5. The
polishing speed ratios R.sub.5/R.sub.1 and R.sub.3/R.sub.1 became
substantially constant between polishing time of 1 and 2
minutes.
In the case of 1.5 minutes polishing time where the pattern width
dependency of the polishing speed becomes constant, the polishing
speed R.sub.1 for a line portion having a line/space width of 1 mm
was 811 nm/min (amount of polishing: 1,216 nm), the polishing speed
R.sub.3 for a line portion having a line/space width of 3 mm was
616 nm/min (amount of polishing: 924 nm), and the polishing speed
R.sub.5 for a line portion having a line/space width of 5 mm was
497 nm/min (amount of polishing: 746 nm), and the polishing speed
ratios R.sub.5/R.sub.1 and R.sub.3/R.sub.1 were 0.61 and 0.76
respectively. In the polishing time of 2 minutes, polishing
advanced to the Al wiring which is a ground under the silicon oxide
film in a line portion of the line/space width of 0.05 to 1 mm.
Comparative Example 2
Polishing of Insulating Film
After an Al wiring line portion having a line/space width of 0.05
to 5 mm and a height of 1,000 nm was formed on an Si substrate
having a diameter of 20.0 mm, a pattern wafer on which a 2,000 nm
thick silicon oxide film was formed by the TEOS-plasma CVD method
was prepared.
2 minutes polishing was performed using a commercially available
silica slurry in the same manner as in the above-mentioned
Examples. The pH of this commercially available silica slurry is
10.3 and the slurry contains 12.5% by weight of SiO.sub.2
particles. The polishing conditions were set to the same as in
Example 1. As in the case of Example 1, the above-mentioned pattern
wafers were polished by setting the polishing time to 3 minutes, 4
minutes, 5 minutes, and 6 minutes.
Using an optical interference type film thickness measuring device,
the thickness difference before and after polishing was measured
and the polishing speed was calculated. The polishing speed of a
line portion having a line/space width of 1 mm is defined as
R.sub.1, the polishing speed of a line portion having a line/space
width of 3 mm as R.sub.3, and the polishing speed of a line portion
having a line/space width of 5 mm as R.sub.5. The polishing speed
ratios R.sub.5/R.sub.1 and R.sub.3/R.sub.1 became larger between
the polishing time of 2 and 5 minutes according to the increase in
the polishing time, and became substantially constant between the
polishing time of 5 and 6 minutes.
In the case of 5 minutes polishing time where the pattern width
dependency of the polishing speed becomes constant, the polishing
speed R.sub.1 for a line portion having a line/space width of 1 mm
was 283 nm/min (amount of polishing: 1,416 nm), the polishing speed
R.sub.3 for a line portion having a line/space width of 3 mm was
218 nm/min (amount of polishing: 1,092 nm), and the polishing speed
R.sub.5, for a line portion having a line/space width of 5 mm was
169 nm/min (amount of polishing: 846 nm), and the polishing speed
ratios R.sub.5/R.sub.1 and R.sub.3/R.sub.1 were 0.60 and 0.77,
respectively. The polishing speed of line portions in each
line/space width for the polishing time of 6 minutes was
substantially the same as in the case of 5 minutes, and it was
found that the polishing advanced at the same polishing speed after
the pattern width dependency of the polishing speed became
constant.
INDUSTRIAL APPLICABILITY
The CMP abrasive according to the present invention can polish a
surface to be polished such as a silicon oxide insulating film or
the like at high speed without causing scratches while attaining
high level smoothing, and has an excellent storage stability.
The method for polishing a substrate according to the present
invention can polish a surface to be polished at high speed without
causing scratches while attaining high level smoothing.
The method for manufacturing a semiconductor device according to
the present invention can manufacture a semiconductor device having
a high degree of reliability with high productivity and good
yield.
The additive for the CMP abrasive according to the present
invention can polish a surface of a film to be polished at high
speed without causing scratches while attaining high level
smoothing, and particularly provide the CMP abrasive with excellent
storage stability.
* * * * *